Power Systems: The Feeds and Speeds

May 5, 2008 Timothy Prickett Morgan

This week, IBM begins shipping the new Power6-based Power 570 and Power 595 servers that support the i, AIX, and Linux operating systems. And Big Blue is in the process of ramping up sales of the entry Power 520, which started selling in AIX and Linux edition in late January and which started shipping in i Editions on April 18, and midrange Power 550 servers, which also shipped earlier this year in an AIX and Linux Edition and which will hit the streets in an i Edition on May 23.

Of course, IBM is also shipping the JS12 and JS22 Power6-based blade servers, which can support the new i 6.1 operating system, formerly known as i5/OS V5R5 for a while and then i5/OS V6R1 when it was announced in January for shipment on March 21. The JS12 and JS22 blade servers require the Virtual I/O server to support i 6.1, and this requires a lot of steps according to the business partners I have talked to–steps that AS/400, iSeries, and System i shops are not used to. The Power6 blades do not support i5/OS V5R4, which came out with Power5+ iron, or even the tweaked version, V5R4M5, which was launched last year so IBM could get a Power6 570 machine out the door that could support RPG and COBOL workloads and run i5/OS and DB2 for i5/OS.

The trouble is, not all of the information about these machines is in one place, despite the Power Systems merger. And I can tell you right now, not all the data is yet available to many end users, even if it is available to Arrow Electronics and Avnet, IBM’s two master server resellers, and is making its way into the hands of myriad downstream resellers who push OS/400, i5/OS, and now i platforms. This makes comparison shopping difficult, of course, and that is why you keep me around. I gather up and compile data because I think it is fun, but I also know what it is like to try to figure out if a server is a good deal or not and I know what it is like to try to run an IT organization–albeit one a heck of a lot smaller than yours–on a tight budget.

To that end, I have been collecting all the information I can get my hands on about the Power Systems servers, and I have created a salient characteristics table for the new machines. I will be compiling more data to make comparisons to the prior several generations of OS/400 and i5/OS servers, and then I will go the extra few miles to compare the new i 6.1 operating system on the Power Systems machines to Windows, Unix, Linux, and mainframe alternatives.

In the table showing the Power Systems iron, items shown in red italics are estimates made by myself in the absence of data. I will update this table as more information becomes available. For instance, Commercial Performance Workload (CPW) relative performance ratings are not available on the Power 595 box, but then again, with i 6.1 not being supported on this machine until September (very likely because IBM is still tuning the operating system and maybe still adding support for features such as Live Application Mobility and Live Partition Mobility, which work with AIX), I don’t expect to see CPW ratings officially until late in the summer when IBM can feel comfortable about saying how much performance this box has running RPG applications against the DB2 for i database.

Because we are now all part of one, happy Power Systems family, I have included IBM’s Relative Performance (rPerf) benchmark ratings for AIX workloads in the table, too, and any other relevant benchmarks I can find that might help you make your plans to upgrade to a Power Systems box or stay in the prior System i line. My guess is that an awful lot of customers will be trying to stick with i5/OS V5R4M5 wherever possible to avoid the application conversion issues associated with i 6.1. With one exception, of course: customers who want to move to blade servers. These customers have no choice but to go to i 6.1, and because life doesn’t have enough irony already, the small and midrange customers who would be most eager to go to the blade form factor because it runs on 120-volt power in the BladeCenter S chassis are the ones who are least happy about making the jump from i5/OS V5R4 to i 6.1.

A few things to bear in mind. First, the i Edition of the Power 520 and 550 machines max out at two and four Power6 cores, respectively, compared to a maximum of four or eight cores for the AIX and Linux Edition of these same machines. None of the boxes have any L3 cache memory on them, which just seems stupid, but IBM is clearly making use of Power6 chips with dud cache memories on in these boxes–and for sound economic reasons in terms of its chip business. Also, the 570-class machine starts out at two cores for the i Edition, but starts out at four cores for the AIX and Linux Edition.

Finally, for customers who are considering the JS12 and JS22 blades, look very carefully at the memory-to-processor and I/O subsystem bandwidth of the raw iron. The blades have substantially less I/O and memory bandwidth than the equivalent i Edition of the Power 520 and Power 550 machines. And those bandwidth numbers are maximum theoretical bandwidth, not actual bandwidth once you throw the Virtual I/O Server on the blade in a partition and have i 6.1 talking to this I/O software translation and virtualization layer instead of directly to the I/O devices through i5/OS microcode. Be very cognizant of the relationship between CPW ratings and your own workloads and how I/O plays into those workloads. You have to be very careful to make sure if you move to the blade servers that you do not end up I/O bound.

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